Launch with ARV

[S2_Dave]

If the ARV gearbox with a decent clutch can take 5k launches on a stock/remapped (let's say homefried) 3B, will the strain really be MUCH greater with a bigger turbo?

The reason I ask is that boost isn't produced until the engine is under load (with Motronic anyway), so whether using a K24 or GT3071 wouldn't the power and torque produced by the engine be roughly the same at the moment the clutch is dropped? I realise that other engine mods will probably have been done alongside a bigger turbo, but those mods without the turbo wouldn't likely make a massive difference, would they?

Is it second gear where the differential in punishment would be greater?

Shout if I've made a stupid assumption along the way .

[Doug_RS2]

It all depends on if you get traction at 5k or get wheelspin - if you get traction you are putting the full torque of the engine through the transmission - your gt3071 should be giving around 480ft'lb+ of torque at 2 bar so you can easily break the box , strip the rear driveshaft splines, or strip the rear diff.

[S2_Dave]

Thanks Doug, I think I get it now... it's not increased 'shock' at the moment the drivetrain is engaged, it's that the torque produced moments after (assuming traction) is already enough to cause the damage. Any idea of the ideal revs to start from with a GT3071 for optimal torque to limit risk of damage but not bog down? Or is it a case of starting low and uping it each time, seeing how brave I am?

[quattronutter]

it could become an expensive test

[Doug_RS2]

I don't really ddo 1/4 miles but i do like launching. I usually launch at revs above where i get traction so it breaks traction and wheelspins - not the fastest but looks and sounds amazing - our cars just move even when they are wheelspinning. When you change into 2nd you don't usually get the wheelspin so you usually find the box or something goes at that point.

Wherever you get maximum torque (maximum boost) you want to laucnh at a few hundred rpm above that and slip the clutch a bit so it does not break traction - but this will abuse the clutch and you need a good one so it grips after a slight slip.

Get a mate to launch your - they usually don't care about you car, and have not spent 1000s on it and will probably be more abusive and get a better launch!

[Rusty]

A bit of water on the road usually helps to kick the back out a little thus adding to the spectacle Or lock the rear diff when exiting a junction and hold on!

Slipping the clutch is really difficult to perfect and does cause some cringe-worthy moments in the process of learning. There was a guy at inters last year who fried his clutch so badly in first that it then didn't grip in second and he limped down the 1/4 with black smoke billowing out from under the car, ouch!

I videoed mine a month or two back and launching at 4.5k with a rapid clutch bringing-up rather than sidestep yielded a 60 time (clocks) of just under 5 with a slight bit of wheelspin, 100 took about 13.5 to 14 (on a private test track of course!). The art is to judge the point at which there is enough load and therefore torque to take the clutch being fully engaged without bogging down and not too much so it spins. I always err on the side of wheelspin but it's usually minimal as I'm close to getting it right. Easy on a k24 with practice, cant imagine Doug's beast being quite so forgiving Suggest that 7k and side-step might work best there and let quattro sort the traction out, I think that was Audiman Tom's method and he fried a torsen rear at Inters

[prosty]

The thing that killed my drivelines was good grip , not the power itself, You can break a diff with stock power and 1.3x 60 foot times with 255x MT DR tyres , if you know your sh*t , or like breaking stuff (like me)

Remember that a spun start is better than a "bogged" one, seeing that when you spin the tyres less stress it put on the driveline than it beeing slowed down fast again, that's atleast my theory

[Fat Audi 80]

You are all

I would never do that in my beloved S2....

[Acidburn]

Mine I have found will spin up really easy even low down in the rev range because of the wheels/tyres i'm running on mine. Atm the clutch has started to complain on the last time I tried it.

I am still deciding which g/b to fit once mine gets removed, i'd kinda like to stick with the 5 speed but it depends how much power it will take.

[Keeper of The Kitten]

Overall car weight imparts load on the entire drivetrain - reduced car weight imparts a reduced load on the drivetrain. You can choose to make the whole car stronger (and heavier) or try reducing the weight to make the car less stressed.

[S2_Dave]

You are all

I would never do that in my beloved S2....

I'm not sure how brave I am, but it's good to get the forum's thoughts just in case :mischeif:. It's never been on a track or strip and they're the only places I would be able to properly play with this toy. There's no money tree in my back garden though, so I have to keep that in mind.

Bringing the clutch up, rather than sidestepping, sounds like a good method of distributing the abuse between gearbox and clutch - it would be great if they both go roughly together in a couple of years' time. Aiming for spin also sounds logical.

I'll be ordering F1 Asymmetrics sometime this week, so grip should be reasonable, but still only 225s (best price I've found is mytyres at £105 per corner incl. delivery and VAT).

If the gearbox does go, I will probably replace it with an older 5 speed rather than a 6 speeder - I quite like the long 3rd gear.

Not much scope for me to lower weight, as I want to keep my creature comforts. I'd like some lighter wheels for my summer tyres, but funds don't allow at the moment. Other things have to take priority (like a good detailing from Steve).

Thanks for the input folks!

Tom managed to last two years without blowing up a 'box, before upping to insane power. Did this two years include any action on a strip?

[jogi730]

On the strip...... think Tom treated anywhere he went as a strip from what I hear
Cheers
CHris